The cross number of a zero-system 
of 
is defined as
 |
The cross number of a group 
has two different definitions.
1. Anderson and Chapman (2000) define the cross number of 
as 
.
2. Chapman (1997) defines 
,
where 
.
A value of the cross number: for a prime 
and 
,
. A stronger statement
is that any finite Abelian group 
is cyclic of prime power order
iff 
.
